The present invention relates to support structures, such as but not limited to those for deploying energy directing surfaces (e.g., reflectors), in either terrestrial or space applications, and is particularly directed to a new and improved compactly stowable support architecture, having both radial and circumferential structural elements, that are configured to be compactly foldable, and to be controllably driven so as deploy an unfurlable medium, such as a mesh-configured reflector.
The use of large reflector structures for satellite communication networks is becoming more widespread as demand for mobile communications increases. As the required aperture size or number of reflectors per space-deployed communication site increases, the availability of lightweight, compactly packaged antenna structures is a key element in continuing industry growth.
A non-limiting example of an umbrella type and folded rib mesh reflector that has been deployed by the National Aeronautics and Space Administration (NASA) for over a quarter of century is the Tracking Data Relay System (TDRS) reflector antenna system. In its deployed state, the metallic mesh reflector structure of the TDRS system measures 4.8 meters in diameter; however, when folded, it readily fits within a cylindrical volume approximately one meter in diameter and three meters in length. Each satellite in the deployed TDRS constellation employs two such antennae. In addition to the TDRS antenna system, commercial mobile communications systems that employ two mesh reflectors, each having an aperture size of twelve meters are also in production. Each of these reflectors, with folding ribs, is sized to fit within a cylindrical volume approximately one meter diameter and four and one-half meters in length. By folding the ribs, the same TDRS-configured volume, moderately lengthened, can package a reflector over twice the TDRS size.
There are varieties of other reflector designs in which rigid elements are oriented in either a radial direction from the reflector center or a circumferential direction at the reflector periphery, and may employ foldable rigid elements to improve packaging. Non-limiting examples of such prior art antenna structures include the following U.S. Pat. Nos. 5,787,671; 5,635,946; 5,680,145; 5,451,975; 5,446,474; 5,198,832; 5,104,211; and 4,989,015.
In now allowed and copending application Ser. No. 09/330,959, a new and improved structure geometry, either deployable or non-deployable, includes both radial and circumferential structural support members to support a reflecting surface, such as a mesh-configured antenna surface. Employing both radial and circumferential support members allows the structure to adapt to a wide variety of geomtries and is not limited to only symmetric structures. The structure can include almost any polygonal shape having a unique geometry at its periphery. As described in that application, the support structure is implemented in either of two embodiments or configurations. Both employ a regular polygonal inner hoop and generally radial struts. The difference between the two configurations involves the location and design of the tips or distal ends of the radial struts.
In the first configuration, distal ends of adjacent radial struts are hinged together in pairs to form the corner of a triangle, a subtended side of which is one side of an interior hoop structure. In the second configuration distal ends of radial struts are not hinged together. Interconnecting distal ends of the radial struts in the first configuration reduces internal member loads for structures having a relatively small (generally less than six) number of sides. The second configuration (where the radial struts are not joined together) facilitates implementing relatively large architectures (having four or more sides); however, there is an increase in internal member loads.
Although the folded reflector package as described in the copending application has a reduced stowed length, it would be advantageous if the stowed length of the folded reflector package could be reduced even more. Also, it would be advantageous if the complexity of the structure could be reduced, especially with regard to the various struts.
The present invention advantageously provides a structural assembly with a reduced complexity and stowed length of a folded reflector package. In one aspect of the invention, the structure assembly includes a rigid hoop structure having a plurality of rigid appendages extending outwardly therefrom and forming struts that are arranged to maintain a prescribed structural periphery depth and radial distance from a center line axis defined by the structural assembly. Each strut is formed from the rigid appendages and includes an optional telescoping tube member. A plurality of pivot elements are distributed within the hoop structure. Interfaces of the hoop structure and the rigid appendages are configured to collapse and deploy the hoop structure. Tension, flexible, generally inextensible cable members are connected to the hoop structure and the rigid appendages.
In yet another aspect of the present invention, the struts include upwardly and downwardly extending struts. The upwardly extending struts can comprise a single strut member or pair of strut members. As a single strut member, the complexity is reduced. The rigid hoop structure can also be formed as a single member hoop structure and the rigid appendages extending outwardly to form the struts can be configured in a triangular configuration. The rigid appendages can also comprise folding hoop members which could also be telescoping tube members.
In yet another aspect of the present invention, a respective pivot element can include a geared power transmission and hinge assembly that is configured to transmit power through a moving hinge to effect opening or closing thereof. It can maintain synchronous motion from one side of the hinge to another throughout all stages of motion of the hinge. Torsion shafts within the rigid elements can transmit power among plural geared power transmission hinge assembles. As compared to the structure disclosed in the copending parent application, the present invention reduces complexity of the structure by collapsing the two upper struts, as shown in FIG. 16, into a single strut. The mechanisms to drive the hinges can be similar in terms of gearing and torsion to drive and the linkage at the corner hinges change slightly to drive only one top strut as opposed to driving two top struts.
The stowed length of the folded reflector package is reduced by introducing the telescoping tube mechanism into top and bottom struts and optionally into the hoop members.